Having the experience (or, love/hate relationship - so awesomely thin and quiet, so underpowered) with 12" Macbook, one surprise is that throttle time really depends on environment temperature and GPU use.

In a cool room it can last few minutes before throttling, while outside on a warm day it throttles almost instantly.

Also, a thermal budget is shared with GPU, so once you plug-in the external display, or start Sidecar, you run out of thermal headspace pretty much instantly.

I'd love to see these two factors tested.